PATHOLOGY - Commercial Broiler Flocks Flashcards
Which diseases are particularly prevelant in commercial broiler flocks?
Dysbacteriosis
Necrotic enteritis
Coccidiosis
Infectious bursal disease
Ascites
Skeletal disorders
Campylobacter
What is dysbacteriosis?
Dysbacteriosis is a disturbance in the gastrointestinal microbiome
What is dysbacteriosis often associated with in broiller flocks?
Stress
Dietary change
Subclinical coccidiosis
What are the clinical signs of dysbacteriosis in broilers?
Foamy faeces
Inappetence
Wet litter
What are the signs of dysbacteriosis on post mortem (PM)?
Undigested feed in the gastrointestinal tract
Orange mucus in the intestines
How do you diagnose dysbacteriosis?
Dysbacteriosis is a diagnosis of exclusion
What can be used to treat and control dysbacteriosis?
Amoxicillin
Probiotics
Organic acids in the water
Manage risk factors
What is the prognosis for dysbacteriosis?
Dysbacteriosis has a high rate of recurrence, especially if the underlying cause/risk factors are not addressed
What is necrotic enteritis in poultry?
Necrotic enteritis is a disease due to enterotoxaemia due to overgrowth of clostridium perfringens in the gastrointestinal tract
|Gram positive, anaerobic bacteria
Why is necrotic enteritis often concurrent with coccidiosis in poultry?
Clostridium perfringens is not very efficient at producing their own amino acids, however, coccidia lyse enterocytes resulting in a release of amino acids into the intestinal lumen which clostridium perfringens can use to proliferate within the gastrointestinal tract
What are the clinical signs of necrotic enteritis in poultry?
Dull
Inappetence
± Diarrhoea
What are the key signs of necrotic enteritis on post mortem (PM)?
Necrosis of the intestinal villi
How can you treat necrotic enteritis in poultry?
Amoxicillin
Probiotics
Control coccidiosis
Why is coccidiosis more prevalent in broiler flocks compared to layer flocks?
Coccidiosis is more prevalent in broiler flocks than layer flocks as layers are typically vaccinated agaisnt coccidia whereas broilers are not
Why are broiler flocks not typically vaccinated against coccidia?
Broiler flocks are not typically vaccinated agaisnt coccidia as vaccination is more expensive than using anti-coccidial drugs, and vaccination can result in a degree of poor performance as the broilers will have to develop immunity, which can reduce growth
What is the main pathogenic significance of coccidiosis?
Coccidiosis is often subclinical and causes poor performance in broilers
How is coccidiosis controlled in broiler flocks?
Anti-coccidial drugs are included in the feed
What is the bursa of fabricus in poultry?
The bursa of fabricus is a primary lymphoid organ in poultry located dorsal to the cloaca and is responsible for the development and maturation of B-lymphocytes
Which pathogen causes infectious bursal disease in poultry?
Avibirnavirus
Describe the pathogenesis of infectious bursal disease in poultry
Avibirnavirus targets the bursa of fabricus where the virus will replicate, resulting in damage and atrophy of the bursa. The destruction of the bursa impairs the production and maturation of B-lymphocytes, resulting in impaired humoral immunity making the bird vunerable to secondary infection
When are poultry typically infected with avibirnavirus resulting in infectious bursal disease?
Avibirnavirus typically infects poultry when the maternally derived antibodies wane
Why is infectious bursal disease more severe in younger birds?
If infectious bursal disease affects birds less than 3 weeks old, their immune systems are still developing and the bursa of fabricus is crucial for B-lymphocyte production and maturation. If this is destroyed, this leads to severe immunosuppression, higher viral replication, and increased susceptibility to secondary infections
(T/F) Infectious bursal disease has a high mortality and low morbidity
FALSE. Infectious bursal disease is very contagious and thus has a high morbildity (appraching 100%), however it has a low mortality
What causes clinical signs seen with infectious bursal disease?
The only clinical signs seen with infectious bursal disease are as a result of secondary infections
What should you be aware of when vaccinating against infectious bursal disease?
The age at which the vaccination against avibirnavirus is administered is crucial. Young poultry are usually vaccinated to help them develop an immunity before they are exposed to the virus, however vaccination has to be timed to avoid interference by the materally derived antibodies which can neutralise the vaccine and prevent the bird from developing their own immune response against avibirnavirus
Why is ascites so common in broiler flocks?
Ascites is commonly a manifestation of right sided heart failure in broiler flocks as they are under a high degree of metabolic stress due to their high growth rates and the heart cannot reach the oxygen demands of the body, resulting in increased cardiac workload which can progress to heart failure. Overall these high oxygen demands result in cardio-pulmonary failure
What are the additional risk factors for ascites in broiler flocks?
High CO2 levels
Low temperatures
Why do high CO2 levels increase the risk of ascites in broilers?
High CO2 levels will further increase oxygen demand and the respiratory rate, increasing metabolic pressure on the heart and lungs
Why do low temperatures increase the risk of ascites in broilers?
Low temperatures will cause the birds to increase their metabolic rate to maintain temperature homeostasis, putting more metabolic pressure on the heart and lungs
What are some of the common non-infectious skeletal problems seen in broiler flocks?
Rotational deformaties
Angular deformaties
Dyschondroplasia
Rickets
What is rickets?
Rickets is a term used to describe soft bones due to an absolute or relative deficiency of calcium or phosphorus or insufficient vitamin D
How can you control rickets?
Ensure there is adequate calcium and phosphorus in the diet
Which pathogens can cause skeletal problems in broiler flocks?
Staphylococcus
Mycoplasma synovia
Reovirus
Enterococcus
Which bone is typically affected by staphylococcus infection in broilers?
Femoral head
What is the significance of campylobacter infection in broilers?
Campylobacter is a commensal bacteria and thus does not cause pathology in chickens however it is zoonotic and can cause disease in consumers if the chicken isn’t cooked sufficiently
